Buzzing Speedometer??

i've seem to stumble on to a problem with my 84 trans am, Just cruising along today and all of a sudden my speedometer starts making this grinding/buzzing noise, and the speedometer is kinda getting almost wavey when it does that.

has anybody else had this sort of a problem ? is the speedometer completly busted or is there pehaps i repair?

My mom used to have a '74 Duster. After a while the speedometer needle just started to slamming itself against the opposite end of the speedometer until it bent so much it looked like the speed needle you'd see in one of those bad SCI-FI movies where the crew passes out, the spaceship then goes out of control and crash lands on some alien world.